The present invention relates to a front section for a motor vehicle, especially passenger motor vehicle, with two longitudinal bearers provided on both sides at a distance to the center longitudinal axis of the vehicle and with one fork bearer each constructed as hollow profile and connecting the longitudinal bearers with a front end wall (firewall) of the passenger cell.
The front section of a motor vehicle body has the task to absorb during normal driving operation the forces emanating from the wheel suspension without permanent deformation, and to absorb the energy occurring in case of an impact of the vehicle by deformation. The forces are thereby transmitted by way of the longitudinal bearer to the fork bearer, are split up by the latter and are further transmitted at suitable points of the vehicle. For that purpose, the fork bearer includes two arms which extend abutting at the end wall, on the one hand, from the longitudinal bearer to the inner tunnel wall and, on the other, from the longitudinal bearer to the front wall column. Additionally, the longitudinal bearer continues up to the sill beam in a third arm starting from the fork bearer abutting at the underfloor of the vehicle. As a result thereof, the force occurring in case of an impact is split up in an appropriate manner and is transmitted at different points of the vehicle (DE-OS 27 25 083). The fork bearer is fixed at the front side of the end wall by means of a welded connection and is also connected with the longitudinal bearer. By reason of the fork bearer constructed as hollow profile, the disadvantage results with the prior art construction that for the fastening thereof at the end wall a large number of individual parts are necessary and several longitudinal welding seams must be provided for the connection of the same.
The present invention is concerned with the task to so construct the aforementioned front section of a motor vehicle that it can be manufactured cost-favorably and rationally with a small number of parts, and that it offers a high degree of safety for the vehicle passengers in case of an impact.
The underlying problems are solved according to the present invention in that the end wall is divided horizontally into an upper part and into a lower part, in that the fork bearer is made of an upper shell and of a lower shell and in that a shell of the fork bearer is made in one piece with the lower part of the end wall.
The end wall now consists of an upper part and of a lower part, whereby the lower part forms at the same time a shell of the fork bearer consisting of an upper and of a lower shell. The upper shell as also the lower shell of the fork bearer can thereby be formed-on at the lower part of the end wall. This construction offers the significant advantage that for the formation of the fork bearer, exclusively the corresponding shell has to be emplaced and has to be connected with the shell formed-on at the end wall, for example, by a welding seam. By forming-on one shell at the end wall, on the one hand, a welding seam extending longitudinally over the end wall is economized and, on the other, a greater rigidity of the fork bearer and of the end wall is achieved. In addition to the greater safety resulting therefrom for the persons present in the passenger cell, also manufacturing costs are economized and, furthermore, the manufacturing time is reduced.
One advantageous embodiment according to the present invention provides that the end wall upper part is constructed in one piece with the upper shell of the fork bearer and the end wall lower part is constructed in one piece with the lower shell of the fork bearer. Additionally, provision may be made that the end wall upper part and the end wall lower part have different sheet metal thicknesses. The utilized sheet metal panels or plates can now be matched as regards their thickness to the required conditions resulting from an impact. Advantageously, the lower part of the end wall will thereby have a greater sheet metal thickness than the upper part because the lower part of the end wall has to absorb a greater amount of energy. The use of sheet metal panels or plates of different thicknesses has advantageously as a consequence a saving in weight because only those sheet metal parts have deliberately a greater sheet metal thickness which are exposed to higher deformations, which have to absorb the predominant part of the energy, and which partition the passenger cell with respect to the engine space.
In another embodiment of the present invention, provision is made advantageously that the end wall lower part with formed-on fork bearer shell is made of a left and of a right half which are joined in the longitudinal center axis of the vehicle. The half of the end wall lower part, which faces the oppositely directed traffic, has thereby advantageously a greater sheet metal thickness. As a result thereof, a different shape-change resistance of the entire end wall is achieved which entails advantages in case of an offset crash because the vehicle side facing the oppositely directed traffic has to absorb, as a rule, a greater amount of energy which is achieved by the reinforced construction of the corresponding end wall lower part. This construction also brings about a weight reduction of the entire end wall because the other half can be made of a sheet metal part with lesser thickness.
Furthermore, the present invention relates to a method for manufacturing a front section of the aforementioned type whereby the right end wall lower part with formed-on fork bearer is deep-drawn in one piece in pot shape in the form of a right and left half, the deep-drawn pot is subsequently split by a longitudinal cut into the right and the left half of the end wall lower part, subsequently the two halves are folded each through 90.degree. about a vertical pivot axis and after the alignment into the final position, are joined together in the center longitudinal axis of the vehicle into the end wall, for example, are welded together, respectively, spot-welded together or the like.
This method for the manufacture of the end wall according to the present invention with formed-on fork bearer shell offers the significant advantage that a shape particularly suited for the deep-drawing, namely, a pot-shape can be used, in connection with which during the deep-drawing the material can continuously flow from the edge, from which results a uniform wall thickness, and in which small material losses as a result of sheet metal scraps occur. The pot resulting after the deep-drawing operation is divided by a longitudinal cut so that two top halves result which represent the end wall halves bulged out toward the front side. These halves, after they are folded apart each through 90.degree. and after the bulged-out parts have been aligned in the direction toward the vehicle front side, are welded together at the center longitudinal axis of the vehicles, that is, at their mutually facing sides, into the end wall. This end wall formed by the pot halves includes at its top side the lower shell or the upper shell of the fork bearer. In addition to the advantage of the optimum utilization of the sheet metal panel or plating utilized during the deep-drawing, the method according to the present invention additionally entails the advantage that the tools for the deep-drawing installation have a simple shape and can therefore be manufactured cost-favorably.
In another embodiment according to the present invention, provision is made that the end wall lower part with formed-on fork bearer shell is constructed in the form of a left and a right half, whereby two right halves, respectively, two left halves each are deep-drawn into pot shape, and the deep-drawn pot is split by a longitudinal cut into the two right, respectively, two left halves of the end wall lower part and after the alignment into the final position, a right half and a left half are joined together in the center longitudinal axis of the vehicle.
In this method according to the present invention, the deep-drawn pot, unlike with the method described hereinabove, does not form a left and a right half of the end wall, but it forms two right or two left halves. Accordingly, two deep-drawing installations must be provided whereby the right halves of the end wall are manufactured with one deep-drawing installation and the left halves of the end wall are manufactured with the other deep-drawing installation. The manufacture of the two halves in different deep-drawing installations offers the advantage that different sheet metal panels, for example, with different thicknesses can be utilized for the halves and, as a result thereof, an end wall can be manufactured suitable for an offset crash. After the deep-drawing of the pots, the latter are also to be split by means of a longitudinal cut into two pot halves each, whereby the pot halves then represent the right or left end side halves which are to be connected with each other by a welded seam.
Provision may also be made according to the present invention that a right and a left half of an end wall with a predetermined sheet metal thickness are made by means of one first deep-drawing tool and also a right and a left end wall half, however, with a different wall thickness, are made by means of a second deep-drawing tool and after the dividing of the deep-drawn pots, for example, a thick right half is connected with a thin left half, and the thin right half with the thick left half into an end wall. The end walls resulting therefrom are suitable for the use in vehicles for right-hand traffic, respectively, left-hand traffic for the optimum energy absorption in case of an offset crash.